In the field of digital radiography a wide variety of image acquisition techniques have been developed that render a digital representation of a radiation image.
In one of these techniques a radiation image, for example an X-ray image of an object, is stored in a screen comprising a photostimulable phosphor such as one of the phosphors described in EP-A-503 702.
In a read out station the stored radiation image is read by scanning the screen with stimulating radiation such as laser light of the appropriate wavelength, detecting the light emitted upon stimulation and converting the emitted light into a digital signal representation that can be subjected to different kinds of image processing techniques.
The original or enhanced image can then be transmitted to a hard copy recorder for reproduction of the image on the film size and lay-out of the radiologist's choice and/or it can be applied to a monitor for display.
It can also be processed and evaluated in a review station and/or archived in an archive station.
After read-out the residual image left on the photostimulable phosphor screen is erased so that the screen is again available for exposure.
As in conventional radiography the radiographic image needs to be associated with a patient. Further, adjustment parameters for the components of the read out device as well as parameters to be used during image processing are to be defined and associated with the radiographic image.
The currently used identification system operates as follows.
A photostimulable phosphor screen is conveyed in a cassette that is provided with an EEPROM having a number of electrical contacts for power supply and read-write transfer of identification data.
The radiologist or operator performs a radiographic exposure of a phosphor screen in the cassette and feeds the exposed cassette into an identification station so that mechanical contact is made between the electrical contact points of the EEPROM on the cassette and contact pins in the identification station.
Then, the identification data of the patient are entered via keyboard into an identification program running on the identification station.
Alternatively, in case the identification station is connected to a hospital information system (HIS) or a radiology information system (RIS), the identification data can be retrieved from the RIS/HIS and entered automatically.
They can be retrieved via a file of known format transmitted over a computer link as has been described in EP-A-674 187.
Further, an examination type identifier is entered. This is performed by selecting a specific examination type (and subtype) out of a hierarchically popped up menu that is displayed on the screen of the identification station.
With an examination type identifier several settings for the read out apparatus, parameters to be used during image processing and parameters that relate to image reproduction etc. are linked. The set of settings and parameters was stored in advance in each of the stations where it is to be used according to a customisation procedure as has been described in EP-A-679 909.
Then, the patient identification data and the examination type identifier are written into the EEPROM on the exposed cassette by means of dedicated hardware linked to the identification station's computer. Further details on this procedure as well as on the outlook of the cassette are described in U.S. Pat. No. 4,960,994.
The exposed and identified cassette is then fed into a read out station where the data stored in the EEPROM are read.
Next the radiographic image stored in the photostimulable phosphor screen is read taking into account the settings for the read out apparatus that correspond with the identifier read from the EEPROM.
The read out image is further subjected to processing taking into account the processing parameters corresponding with the identified examination type.
Next, the screen is erased and at least some of the data stored in the EEPROM are erased (or updated).
Since the identification system makes use of an EEPROM requiring mechanical contact for data and power transfer from the identification station, the system is not adapted for portable identification.
An alternative identification method and system has been developed which is suitable for portable identification. This method and system is described in EP-A-727 696.
According to the method described in this patent application patient identification data are entered into an identification station, e.g. at a take-in desk located at the entrance of the hospital.
Next a patient identification means such as a bracelet or a batch is produced. The data entered into the identification station is transferred to the patient identification means.
The procedure followed to identify a radiographic image comprises the following steps. First the patient identification data are read by means of a (portable) read/write device from the patient's personal identification means (from the badge, bracelet etc.). Then, examination type data and/or other type data are entered to this read/write device.
The data are associated with the patient identification data. Finally, these data are written by means of a suitable probe provided on the read/write terminal onto a radiofrequency tag which is provided on or can be attached to a cassette conveying a photostimulable phosphor screen or alternatively a radiofrequency tag that is embedded in the photostimulable phosphor screen.
This system requires the production of an identification means (badge, bracelet etc.) for each patient. Identification data are to be entered at the identification station, transferred onto a patient identification means, read again by a (portable) read/write terminal, temporarily stored and finally transferred from the read/write terminal to the information carrier on the cassette. The method is thus complex and demands a lot of interaction by the operator.
The system furthermore requires that a read/write terminal is provided which has the capability of reading data from the information carrier on which the patient identification data are written and of writing data onto a radiofrequency tag.
In an alternative short cut embodiment of the above-described method, the patient identification data are retrieved by the (portable) read/write terminal from a radiology information system (RIS) or a hospital information system (HIS). Next, these data are written by the (portable) read/write terminal onto a radiofrequency tag provided on or attachable to a cassette conveying a photostimulable phosphor screen.